Transducers with periodic ferroelectric polarization are widely used in multiple applications with a high operating frequency, for example as resonators playing the role of impedance elements with strong electromechanical coupling for applications to frequency filters, as filtering elements in an oscillation loop for applications to radiofrequency sources, and generally as passive components for radiofrequency signal processing applied to sensors. It should be noted that structures with periodic ferroelectric polarization were initially applied for optical components of the frequency doubler type and as such, they have been optimized in terms of technological achievement.
According to documents WO 02/07310 A1 and WO 2010/031924 A1, it is known how to produce in a planar way piezoelectric transducers with periodic ferroelectric polarization, i.e. having alternating ferroelectric domains. These transducers give the possibility of generating, sustaining and detecting elastic waves guided between two metal surfaces, for which the phase velocities are of the order of 3,800 and 6,500 meters per second, and which are compatible with applications of filters and radiofrequency sources. However, such transducers have quite modest electro-acoustic couplings of a few fractions of percent.
Searching for methods for collectively manufacturing a large amount of piezoelectric transducers with alternating ferroelectric domains on a crystal plate remains a topical subject.
The methods developed up to now essentially consist of making use of lapping/polishing plates, attached flat on a supporting substrate, optionally by adhesive bonding.
This approach is certainly very effective but does not give the possibility of easily controlling plate thicknesses of less than 10 μm.
The technical problem is therefore to improve the manufacturing of plates with thicknesses of less than 10 μm, or in other words improve the manufacturing throughput of plates of piezoelectric transducers with alternating ferroelectric domains for which the thickness is less than 10 μm.
Related, another technical problem is also to improve the integration of several transducers with periodic ferroelectric polarization produced on a same crystal wafer.
Another technical problem is to be able to produce transducers with alternating ferroelectric domains giving the possibility of obtaining higher electro-acoustic couplings.